The performance of internal combustion engines may be enhanced with forced induction, such as, for example, supercharging or turbocharging. Forced induction devices, such as superchargers or turbochargers, are essentially air compressors that force more air into the combustion chambers of an engine than the engine could otherwise draw in on its own. With this increased air, more fuel may be injected to create a balanced, but more potent air-fuel mixture. This air-fuel mixture may combust more forcefully, thus enabling the engine to produce more power.
Forced induction devices may include turbine wheels and/or compressor wheels that spin to compress intake air, and thus, increased air flow to the engine. These wheels, however, have mass, and therefore, inertia. The ability to overcome this inertia and get these wheels spinning (“spool up”) can be a substantial factor in the responsiveness of the engine. That is, the faster the forced induction device can accelerate these wheels, the more responsive the engine may be. In addition, faster acceleration of these wheels enables transient emissions (i.e., emissions created by other than steady state engine operation, such as acceleration or constant rpm with increasing load) to be better controlled with less sacrifice of engine performance. The air-fuel ratio may be maintained while rapidly increasing fuel supplied to the combustion chamber if the forced induction device can spool up quickly to match the increased fuel with increased air. The ability to maintain a desired air-fuel ratio allows for better emissions control. It may be desirable, therefore, to reduce the mass of these wheels in order to reduce their inertia and allow for faster spool up.
Forced induction systems have been developed that use more than one forced induction device (e.g., twin-turbos). By using two smaller turbos, instead of one large one, the twin-turbos may spool up faster because the two smaller compressor wheels may be less massive than the single large one. These types of systems, however, could still benefit from lighter components. Further, a system with multiple forced induction devices may be more costly and/or complex to produce and maintain.
Wheels for certain types of devices have been developed with hollow inner geometry in order to reduce mass and/or allow for passage of fluid through them. For example, U.S. Pat. No. 6,454,533, issued on Sep. 24, 2002, to Beyer (“the 533 patent”), discloses a hollow wheel for a hydraulic turbine. The wheel of the '533 patent, however, is designed for a hydraulic turbine that spins at about 90 rpm. In contrast, forced induction devices can spin at speeds up to 200,000 rpm. These high rotational speeds call for utmost precision in the manufacturing process to insure the structural integrity of the component under such high demands. Some manufacturing techniques, such as casting, have limitations with regard to the precision and/or kinds of structures that they are capable of producing. Innovative casting techniques have been developed, but may be complicated and/or cumbersome.
The disclosed power system component is directed toward overcoming one or more of the problems set forth above.